There is a growing need for large lenses, such as large objective lenses for astronomical telescopes, projection lenses for television receivers, aerial camera lenses, satellite camera lenses and concentrating lenses for solar generating devices. The manufacturing of such large lenses by conventional methods involving the grinding and polishing of glass is exceedingly expensive and time-consuming.
The simple objective of the present invention is to provide large optical lenses of a quality which will satisfy many applications including those enumerated above and which can be produced without any grinding and polishing operations whatsoever, thus drastically reducing the cost of the lens.
Another object of the invention is to provide a lens whose focal length can be easily and quickly adjusted.
In accordance with the invention, these objectives are achieved by use of a variable chamber adapted to be filled with an optically clear fluid, liquid or gaseous, the pressure of which fluid is regulated by adjusting the volume of the chamber containing it. The chamber is closed at opposite ends by resilient optically clear diaphragm elements which bend or bulge with varying degrees of curvature responsive to pressure changes induced in the fluid within the chamber to thereby establish the optical parameters of the lens. Typically, a pair of axially adjustable threaded telescoping sleeves define a chamber for a suitable optical fluid, the opposite outer ends of the chamber being closed by a pair of relatively thin resilient optical discs formed of available plastics material. The discs have their curvatures altered in response to changes in pressure in the fluid filling the chamber. Two or more spaced discs can be employed in the system.
Other features and advantages of the invention will become apparent during the course of the following description.